[systoll]

It's an interaction between user preferences, equipment, configuration, and environment, and we don't really have the information to cut through all that.

An HDR monitor displaying ~1000 nits on black in the dark room is great for film, but no-one would want to read text like that. On the other end of the scale, if you're out in the sun, trying to eek out as much time out of your iPhone as possible, you've probably set the brightness so that you can deal with black on white, but reducing it further would be unwanted.

You can't know what your users are actually seeing, and even if you could, there's a layer of personal opinion on top of all that.

IMO, the only reasonable assumption you can make is that most people have their devices set up so that they're happy with the OS itself -- and every mainstream OS [but especially iOS] uses a ton of #000 on #FFF.